U.S. patent number 3,613,539 [Application Number 04/747,996] was granted by the patent office on 1971-10-19 for integral photography.
Invention is credited to Leslie Peter Dudley.
United States Patent |
3,613,539 |
Dudley |
October 19, 1971 |
INTEGRAL PHOTOGRAPHY
Abstract
Photographs of the integral type, exhibiting the effect of
parallax about both horizontal and vertical axes, are recorded on a
spherically lenticulated film or a spherically lenticulated
screen-film combination by means of a modified type of camera.
Light is admitted to the film via a rectangular aperture in the
front of the camera instead of via the usual photographic
objective. If the camera is held stationary during an exposure, the
resulting photograph is pseudoscopic instead of stereoscopic. A
feature of the invention is a method, comprising a sequential
printing technique, by which the elementary images constituting the
composite picture are so transposed that the reproduction is
stereoscopic. Another feature of the invention involves lateral
movement of the camera during an exposure so that the necessary
transposition is accomplished within the camera. Further features
of the invention reside in methods of increasing the effective
stereoscopic base of the integral photographic system and methods
of adapting the system to aerial photography.
Inventors: |
Dudley; Leslie Peter (Los
Angeles, CA) |
Family
ID: |
25007544 |
Appl.
No.: |
04/747,996 |
Filed: |
July 26, 1968 |
Current U.S.
Class: |
396/661 |
Current CPC
Class: |
G03B
35/24 (20130101) |
Current International
Class: |
G03B
35/18 (20060101); G03B 35/24 (20060101); G03b
035/08 () |
Field of
Search: |
;355/33 ;350/167
;95/18P,1 ;88/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Horan; John M.
Assistant Examiner: Clement; D. J.
Claims
I claim:
1. A photograph of the integral type comprising backing means
supporting an image-recording layer on which is recorded an array
of elementary images of different aspects of the same scene, the
aspect of the scene represented by each such elementary image being
dependent upon the location of that image with respect to the
others in the array, the individual elementary images being so
positioned that, whereas each such image is correctly oriented with
respect to its horizontal and vertical axes, and whereas the images
are arranged in sequence along the horizontal axis of the array so
that those images corresponding to more leftward aspects of the
scene are reproduced in the left-hand portion of the array and
those images corresponding to more rightward aspects are reproduced
in the right-hand portion of the array, the said images are
arranged in sequence along the vertical axis of the array so that
those images corresponding to upper aspects of the scene are
reproduced in the lower part of the array and those images
corresponding to the lower aspects of the scene are reproduced in
the upper part of the array.
2. The photograph claimed in claim 1, and which includes a
transparent viewing screen applied to the surface of said
photograph, the viewing screen having lenticules of substantially
spherical curvature formed on the front surface thereof, the rear
surface being in contact with the image-recording layer, the said
image-recording layer being located substantially at the focal
plane of said viewing screen.
3. The photograph claimed in claim 2, and which comprises a
composite structure, the image-recording layer being a
photosensitive layer applied to one surface of a transparent
photographic film base the opposite surface of which has spherical
lenticules formed thereon.
Description
The present invention is concerned with an improved system of
stereoscopic or three-dimensional photography. A photograph
produced in accordance with one or another of the methods described
in this specification exhibits optical characteristics closely
resembling those of a hologram. Thus, the aspect of the recorded
three-dimensional image changes with change of viewpoint about both
horizontal and vertical axes. However, the new type of photograph,
which may be appropriately termed an integram or integraph,
possesses several important advantages over the hologram. For
example, coherent light e.g. laser illumination) is not required in
either taking or viewing the picture. Further advantages are: the
photographic equipment employed is compact and simple to operate;
exposure times correspond to those which would be required for
ordinary two-dimensional photography under the same conditions;
action shots and/or the use of flash present no more difficulty
than with ordinary photography, and it is virtually impossible to
produce an out-of-focus picture.
The photographic record constituting an integram consists of a
large number of minute, juxtaposed images produced by an optical
screen or reseau. The same--or a similar--screen is used when
viewing the picture. In the preferred form the screen consists of
transparent material embossed on one surface with an array of small
lenticules or lenslets of spherical or substantially spherical
curvature. The screen is so located with respect to the
photographic film emulsion or other photorecording medium that the
photorecording surface is at the focus of the lenticules. A
convenient arrangement is for the screen-film combination to be
manufactured as a composite unit, the lenticules being formed on
the surface of the film base opposite the surface carrying the
photosensitive emulsion.
In some applications of the present invention it is possible to
employ, instead of a screen embossed with spherical lenticules, a
device which may be regarded as the optical equivalent of such a
screen. One type of optically equivalent screen is made from a pair
of cylindrically lenticulated screens, the lenticulated surfaces of
the two screens being in contact with each other, and the
longitudinal axes of the lenticules of one screen being at
right-angles to the longitudinal axes of the lenticules of the
other screen. Another type of optically equivalent screen consists,
in effect, of a sheet of opaque material pierced with a
multiplicity of small apertures disposed in a regular array. In
this case the apertures are not circular, like a pinhole, but are
so shaped that adjacent images in the corresponding array of images
are not appreciably overlapping or spaced apart; thus, apertures of
square shape are very suitable. A satisfactory square-aperture
screen can be produced by "crossing" two line screens which have an
appropriate opaque/transparent ratio; then, by correct adjustment
of the distance between the array of apertures and the sensitive
surface, matters can be so arranged that adjacent images in the
array are not overlapping or spaced apart by an excessive amount.
There are, basically, two alternative techniques either one or the
other of which may be used for production of an integram; one of
these techniques is termed direct integraphy, and the other is
referred to as indirect integraphy. The present application is
concerned with the direct method, the indirect method being
described in my copending U.S. Pat. application, Ser. No. 747,931,
filed of even date herewith, entitled "Improvements in Stereoscopic
Photography." The method described herein resembles that disclosed
by Gabriel Lippmann in 1908 (C. R. Academie des Sciences, Vol. 146,
pp. 446-51). That is to say, the lenticular film or screen-film
combination is exposed direct without the use of a camera lens. The
film is supported in a suitable camera body or holder during
exposure. The exposure is controlled by the use of a filter or
filters in front of the film and (or) by adjustment of the shutter
speed, the shutter being preferably of the focal-plane type.
A minute image of the entire scene is recorded in the format of
each lenticule, but the aspect of the scene represented by each
such image is dependent upon the location of the associated
lenticule with respect to the other lenticules in the array. Upon
viewing the completed photograph, through the lenticular array, the
eyes perceive the optical reconstitution or integration of the
multiplicity of images which exhibits the form of a single,
three-dimensional image. The degree of parallax exhibited by the
three-dimensional image, about the horizontal and vertical axes, is
governed by the corresponding dimensions of the format of the
screen-film combination. A photograph produced in the simple manner
just indicated, as in the case of one produced in accordance with
Lippmann's proposal, will be seen in pseudoscopic relief instead of
stereoscopic relief. It is a feature of the present invention to
provide means whereby this defect can be overcome so that the
resulting picture exhibits stereoscopic relief and is correctly
oriented. Other features of the invention will become apparent
later in the specification.
Nature of the Lenticules and Method of Manufacture
In the applicant's copending U.S. Pat. application, Ser. No.
747,931, referred to above, there is a detailed discussion of the
optical properties of the individual lenticules and methods of
manufacturing lenticular film and screens suitable for use in
connection with the invention. Such film and screens are also
suitable for use in connection with the invention described herein.
However, it is generally desirable for lenticules designed for use
in the direct method to have a greater acceptance angle than those
used in the indirect method. In the case of the direct method, the
angular coverage of the photographic system is limited by and to
the acceptance angle of the lenticules. On the other hand, in the
case of the indirect method, the angular coverage of the system is
governed solely by that of the camera lens. Thus, the angular
coverage can be varied by the simple expedient of changing the
lens. In most practical cases the angular coverage of the lens is
in excess of the acceptance angle of the lenticules.
In the drawings:
FIG. 1 is a simplified diagram representing a piece of spherically
lenticulated film recording an integral photograph.
FIG. 2 is a perspective view representing a piece of spherically
lenticulated film recording an integral photograph.
FIG. 3 shows the piece of film in FIG. 2, viewed through the
lenticules, subsequent to processing and being rotated through
180.degree. in the image plane.
FIG. 4 represents a contact (emulsion-to-emulsion) print from the
original photograph in FIG. 3.
FIG. 5 represents one type of print which can be obtained, by means
of a two-stage transposition process, from the original photograph
in FIG. 3.
FIG. 6 represents a further type of print which can be obtained, by
means of a single transposition process, from the original
photograph in FIG. 3.
FIGS. 7 through 10 constitute a series of diagrams illustrating the
principle of the transposition process.
FIG. 11 shows a form of camera suitable for taking photographs in
accordance with the invention.
FIG. 12 is a diagram showing an optical method of extending the
stereoscopic base of an integral photographic system.
FIGS. 13a and 13b are diagrams showing mechanical methods of
extending the stereoscopic base of an integral photographic
system.
BASIC PRINCIPLE
FIG. 1 is a simplified diagram representing a piece of spherically
lenticulated film (or screen-film combination) F recording an
integral photograph of an object O. As will be understood, the
lenticules are shown greatly enlarged for the sake of clarity. It
is to be assumed that the diagram represents a plan view, the left
and right edges of the object being denoted by respectively l and
r, the corresponding edges of the film being denoted by l' and r'.
It will be observed that the aspect of the little image formed at
the focus of each lenticule is dependent upon the location of the
lenticule relative to the object, the aspect changing progressively
from an extreme leftward view at the edge l' of the film to an
extreme rightward view at the edge r'. In addition to the single
row of lenticules illustrated, there are, of course, further,
parallel rows of lenticules which must be imagined as disposed in a
plane normal to the surface of the drawing. Accordingly, the images
recorded by the lenticular array differ in respect of both vertical
and horizontal parallax.
Let us now imagine that the processed film is viewed by an observer
located in front of the lenticules at some position such as that
occupied by the object O in FIG. 1. Then the leftward aspects of
the image will lie to his right and will be seen predominantly by
his right eye, while the rightward aspects will lie to his left and
will be seen predominantly by his left eye. In consequence, the
integral image will be seen pseudoscopically. It will also appear
upside down or inverted due to the inversion of each little image
element resulting from the action of the associated lenticule. If,
now, the piece of film be rotated through 180.degree. in its own
plane in order to compensate for this inversion, the integral image
will be laterally inverted or perverted so that it will again be
seen pseudoscopically. In short, in order that the completed
photograph may be seen in stereoscopic relief, it is necessary for
the individual picture elements to be appropriately reoriented or
transposed. The situation is similar to that prevailing when a
simple stereogram or stereoscopic pair of photographs has been
recorded on a single plate or piece of film; the two views, or
reproductions thereof, must be laterally transposed in order that
they may be viewed in stereoscopic relief in a stereoscope.
In order that the integral image shall appear sharp, clear and
undistorted, it is necessary to provide means for avoiding the
formation of secondary or parasitic images. One such means is to
arrange, in the manufacture of the lenticular film or other
screen-film combination, for each lenticule to be isolated from the
adjacent lenticules by a surrounding boundary composed of some
opaque substance. This substance may take the form of a
photographic emulsion, applied to the lenticulated surface in a
thin layer so that it surrounds, without completely covering, the
lenticules. The layer is then exposed to light and chemically
developed in order to render it both black and opaque. As will be
understood, this stage of the manufacturing process is carried out
prior to application of the photorecording layer or layers in those
cases in which the lenticular screen is an integral part of the
film. An opaque layer of this type is represented in FIG. 1 by the
dark areas between the lenticules. As an alternative, or in
addition, to the use of such a layer, it is possible to use a
lightshield or hood extending outward from the edges of the film
format.
The Transposition Process
FIG. 2 depicts, greatly enlarged, a small piece of spherically
lenticulated film recording an integral photograph of some
three-dimensional subject represented by the large letter L, the
general direction of the image-forming rays being indicated by the
arrow. As will be noted, the piece of film is embossed with 16
lenticules, in square array. The elementary images formed by the
lenticules are numbered consecutively from 1 to 16. Images Nos. 1,
5, 9 and 13 represent the extreme leftward aspects of the subject;
Nos. 4, 8, 12 and 16 represent the extreme rightward aspects; Nos.
1, 2, 3 and 4 represent the extreme upper aspects; Nos. 13, 14, 15
and 16 represent the extreme lower aspects, and Nos. 6, 7, 10 and
11 represent intermediate aspects, as will be understood. If the
processed film, erected in order to compensate for the
image-inversion due to the action of the lenticules, is now viewed
through the embossed surface, the orientation of the elementary
images will be as shown in FIG. 3; thus, the images will be
laterally inverted or perverted, in consequence of which the
integral image will be pseudoscopic. A further point, but one of
minor consequence, is that the effect of vertical parallax will be
exhibited in a manner opposite to that occurring in everyday visual
experience. This is due to the interchanging of the horizontal rows
of images as indicated in the drawing. A contact
(emulsion-to-emulsion) print from this photograph onto a second,
matching piece of lenticular film will bring about the result
represented by FIG. 4. In this case the integral image will again
be pseudoscopic since, although each individual elementary image is
correctly oriented, the leftward aspects are located to the right
of the observer, and the rightward aspects are located to his left.
Vertical parallax will be exhibited in the same manner as by the
arrangement shown in FIG. 3. Clearly, the ideal or perfect solution
to this problem would be provided by (a) rotation of each
elementary image through 180.degree. within its own format,
followed by (b) the making of a contact (emulsion-to-emulsion)
print. This would yield the arrangement shown in FIG. 5, resulting
in an integral image which is stereoscopic and free of error in
respect of vertical parallax. However, as discussed at length in
the applicant's copending U.S. Pat. application, Ser. No. 747,931,
it is a demonstrable fact that stereoscopic photographs which
exhibit reversed vertical parallax are entirely acceptable to the
observer; indeed, this type of defect will generally pass
completely unnoticed. Thus, the arrangement of the elementary
images which is represented in FIG. 6 also constitutes a
satisfactory integram, as the resulting integral image is correctly
oriented and stereoscopic. Means whereby integrams of the types
represented in both FIGS. 5 and 6 can be produced constitute
features of the present invention.
The transposition process with which the invention is concerned
involves a sequential printing technique which can be followed with
the aid of FIGS. 7 to 10. These four schematic drawings represent a
time-spaced sequence of steps by which the original integral
photograph in FIG. 3 can be used to print the integram represented
in FIG. 6.
Referring to FIG. 7, the original photograph, denoted by O, is
placed in emulsion-to-emulsion contact with the matching piece of
lenticular material P on which the reproduction is to be printed,
the left-hand column of lenticules on O being opposite the
right-hand column of lenticules on P. The general direction of the
printing light rays is indicated by the arrow A. The width of the
strip of emulsion being exposed is restricted to the lenticular
pitch distance; this can be accomplished by any suitable means,
such as by admitting the light via a narrow slit, narrow
cylindrical lens, or other convenient arrangement. Thus, in FIG. 7,
just those images numbered 16, 12, 8 and 4 are printed. Referring
now to FIG. 8, it will be noted that the photograph O has been
transported to the left through a distance equal to the lenticular
pitch, and that the film P has been transported to the right
through the same distance; accordingly, the images numbered 15, 11,
7 and 3 can now be printed to the left of the column of images
first reproduced. In FIG. 9 the two pieces of photographic material
are depicted as having been again transported, in opposite
directions, through a distance equal to the lenticular pitch,
making it possible for the third column of images to be printed.
FIG. 10 shows, finally, the printing of the fourth and last column
of images, the completed integram now being of the type represented
in FIG. 6.
The foregoing method of accomplishing the desired result has been
selected for description simply as an example of the general
principle involved. Various modifications of the technique are
possible. The essential feature is that, between successive steps
in the printing operation, there must be relative movement between
the two films, plates or the like through a distance equal to twice
the lenticular pitch. Accordingly, it is not necessary for both
pieces of photographic material to be transported laterally. Thus,
the piece denoted by P in the diagrams can be held stationary while
that denoted by O, together with the printing aperture or
equivalent, is transported laterally through twice the distance(s)
indicated in the preceding explanation of the process. In the
method preferred by the applicant, the piece of photographic
material O, together with the printing aperture, is held stationary
while the piece of photographic material P is transported.
If desired, the aforementioned relative movement between the two
pieces of photographic material can be intermittent, printing light
being admitted only during the stationary periods. However, the
applicant considers it to be more practical and convenient for the
movement to be continuous; the light source (e.g., electronic
flash) is so synchronized with the film transport mechanism that a
light pulse is emitted each time the film has moved through the
prescribed distance. Provided that the duration of a pulse is a
small fraction (e. g., one-hundredth) of the time taken by a
lenticule to move past the printing aperture, no perceptible
image-smear will result. As an alternative to electronic flash, a
source of continuous illumination can be employed, the light being
occulted intermittently by means of a synchronously driven shutter,
or switched on and off by a synchronously operated commutator
device.
By repeating the transposition process, but using a vertical scan
instead of the original horizontal scan, an integram of the type
shown in FIG. 10 (or FIG. 6) can be converted into one of the type
shown in FIG. 5. However, for the reason previously indicated, this
second scanning operation is considered to be unnecessary in the
majority of practical applications of the process.
No basically new mechanism is required in order to accomplish the
transposition process. The accurate transport mechanism which is
necessary is available in, for example, ruling engines of the types
used for producing fine-pitch line screens and diffraction
gratings. (A portion of a typical ruling engine, modified for the
manufacture of spherically embossed lenticular film, is illustrated
in the applicant's copending U.S. Pat. application, Ser. No.
747,931.) To one skilled in the art, the provision of the necessary
light-tight enclosure, film platens, illuminating means, etc., will
not present difficulty.
Copies of integrams of the types represented in FIGS. 5 and 6 can
be made by any of the techniques described in the patent
application mentioned above.
Camera for Recording Integral Photograph
FIG. 11 shows an example of an instrument for use in
image-recording in accordance with a feature of the invention. This
can be either an instrument designed specifically for the purpose
or, alternatively, a regular camera which has been appropriately
modified.
Although no camera lens is used, it is necessary that the equipment
employed shall embody certain physical and mechanical features
which are common to the majority of regular photographic cameras.
The main features which are considered to be essential are the
following: a housing (e.g., camera body), container or film holder
for supporting the film or other photosensitive material during
image-recording, and for protecting said material from
unintentional exposure to light; some means (e.g., variable-speed
focal plane shutter) of admitting a controlled amount of light from
the subject to the photosensitive surface via the lenticules; means
(e.g., film-advance mechanism or a set of cut-film holders) for
bringing a fresh, unexposed area of photosensitive material into
position after an exposure has been made, and some form of
viewfinder.
Consider now that the sketch of FIG. 11 represents a camera,
designed originally for use with 35 mm. or, say, 21/2, inch-wide
roll film. Assume, further, that the camera is equipped with a
focal plane shutter, actuated by the shutter-release button 4. The
film-advance and shutter-cocking lever is denoted by the numeral 1
in the sketch, 2 denotes the shutter speed-adjustment knob, 3
denotes the viewfinder, and 5 denotes the film-rewind knob and
lever. (The latter control is, of course, required only if
cassette-loading is employed.) As will be noted, the camera lens
has been removed, and it is to be assumed that a rectangular
aperture a b c d has been cut in the front of the camera body. The
width (major dimension) of this aperture is preferably about equal
to the length of that portion of film which extends between the two
spools and is held flat in the focal plane. Thus, the width can be
assumed to be somewhat greater than that of the picture format for
which the camera was originally designed. For the sake of
simplicity, it will be assumed that the width is equal to twice
that of the original format.
In the example arrangement illustrated, two equal rectangular
portions at the left and right sides of the aperture have been
closed by the insertion of a pair of opaque plates 6 and 10. These
plates can be easily removed, when required, for a purpose to be
described later. A further, larger plate 7 is inserted between
plates 6 and 10, a rectangular or square aperture 8 having been cut
in the center portion of this larger plate. The dimensions of this
aperture are substantially the same as those of the original
format. Into this aperture is inserted a thin walled, framelike
component 9 which protrudes outward from the camera body for a
short distance and inward so that the rear edges are in contact
with a sheet of clear glass. This sheet of glass, the surfaces of
which are preferably optically coated, extends over the entire area
bounded by the rectangle a b c d. The purpose of the glass is to
protect the shutter, film, etc., against ingress of dust or other
extraneous matter. The portion of the frame 9 which protrudes
outward from the camera body can, if desired, be slotted to receive
filters of various types, such as color filters, polarizing
filters, etc. An additional, desirable accessory, denoted by 11 in
the sketch, is a sun shield designed for fitting around, and
attachment to, the front portion of the frame 9.
Modified as shown in FIG. 11, the equipment is now adapted for
recording, on suitable spherically lenticulated film, integral
photographs each of which will be constituted of an array of
microscopic images extending over an area of film corresponding to
that of the original format. As will be understood, the magnitude
of the three-dimensional effect will be governed by the
dimensions--primarily the horizontal dimension--of that format.
Now, in the case of a camera of the type illustrated, the length of
that dimension will generally be less than 21/2, inches, so that
the three-dimensional effect will be less than normal. However, the
stereoscopic base can be increased, if desired, with the aid of the
removable plates 6, 7 and 10 in the manner now to be described.
On the basis of the assumption, made previously, that the
horizontal dimension of the rectangular aperture a b c d is equal
to twice the width of the original format, it follows that removal
of plates 6, 7 and 10 will double the length of the strip of film
exposed when the shutter is actuated. Accordingly, the amount of
horizontal parallax, and hence, the three-dimensional effect, will
also be doubled. The number of exposures that can be made on a
given length of film will, of course, be halved. If the instrument
employed is a regular camera which has been modified, rather than
an instrument which has been designed specifically for the present
purpose, there are some further points to be borne in mind if the
feature just described is to be utilized. For example, the width of
the gate aperture will generally have to be increased; so, too,
will the distance traversed by the focal plane shutter. Another
point relates to the feature--common to many so-called miniature
and small-format cameras which provides interlocking of the
film-advance (and shutter-cocking) lever and the shutter-release
button. The interlocking mechanism prevents double exposure on a
single frame of film, and also obviates film wastage by preventing
the operator from advancing a further frame of film into position
until the shutter-release button has been pressed. Hence, in order
to make a series of exposures each of which occupies a length of
film equivalent to two regular frames, we can adopt one or the
other of two procedures. One of these procedures is to modify the
mechanism in such a way that the film-advance and shutter controls
can be operated independently; the film can then be advanced
through the required distance equal to the width of two regular
frames without the necessity for pressing the shutter-release
button after the film has moved through one-half of that distance.
The other, more simple, procedure involves no modification to the
camera mechanism; it involves merely the provision of an opaque
mask or blind for occulting light from the aperture a b c d when,
after the film has moved through one-half of the total required
distance, actuation of the shutter is rendered necessary by the
interlocking mechanism. Just as it is desirable for a frame 9 and
sun shield 11 to be employed in conjunction with the small aperture
8, so, too, is it desirable for a larger, appropriately shaped
frame and sun shield to be used in conjunction with the aperture a
b c d. With the plates 6 and 10 in position, as indicated in the
sketch, but with the plate 7 removed, it will be evident that the
area of film occupied by each exposure is greater than that of the
original format but less than that of the aperture a b c d. It is,
of course, desirable for an appropriately shaped frame and sun
shield to be used in conjunction with this intermediate-sized
aperture also.
If an intermediate-sized aperture, as indicated above, is to be
employed, it is preferable for the entire apparatus to be specially
designed; in modifying a regular camera to include this feature, it
is likely that problems will arise in connection with the film
transport mechanism, frame counter, etc.
Use of Auxiliary Optical System
FIG. 12 is a schematic diagram showing how the stereoscopic base of
an integral photographic system can be extended beyond the limit
imposed by the dimensions of the film or image format.
Referring to the sketch, S denotes a spherically lenticulated
screen the transverse dimensions of which are relatively large
compared with those of the image format F. The screen forms a
multiplicity of small images, at its focal plane, of the complete
scene or subject. This array of images is reproduced, to a reduced
scale, in the format F of the lens L.sub.2. It is preferable for a
field lens L.sub.1 to be located at, or in close proximity to, the
focal plane of the screen S. As will be understood, the
image-recording medium at F may be photographic film, the
photosensitive face of a television camera tube, or any other type
of image-recording or image-receiving medium.
Use of an auxiliary optical system, in the way indicated above,
does not change the nature of the integral image from pseudoscopic
to stereoscopic; this is because introduction of the lens L.sub.2,
with or without the field lens L.sub.1, simply causes inversion of
the array of elementary images as a whole, and does not cause
inversion of each elementary image within its own individual
format. Hence, transposition of these images must still be
accomplished by, for example, the sequential printing process
described earlier in the specification As an alternative to that
process, an electronic scanning technique or its optomechanical
equivalent (i.e., scanning by means of a lightspot instead of an
electron beam) can be employed. Transposition by scanning is
particularly useful in television applications of the invention.
Thus, an image formed in, say, the upper left-hand corner of the
format of a television camera can be reproduced, after transmission
to a television receiver, in the corresponding corner of the
picture tube or in any one of the other three corners, depending
upon the arrangement of the scanning circuitry. As will be
understood, the faceplate of the picture tube of the receiver must
be embossed with lenticules distributed in an array which
corresponds with the lenticular array used in transmission. This
matter and related topics are discussed in more detail in the
applicant's copending patent application to which previous
reference has been made.
Referring, once more, to FIG. 12, when the image format at F is
that of a television camera tube, it is, of course, unnecessary for
the faceplate to be lenticulated. If, however, the format at F is
that of a piece of photographic film or the like, the material may
be either lenticular or nonlenticular depending upon the manner in
which it is to be treated after exposure and processing. For
example, assuming a regular photographic plate is employed, the
orientation of the elementary images recorded will be as shown in
the earlier diagram FIG. 3. These images can then be reoriented, by
the transposition process already described, in the way shown in
FIG. 5 or that shown in FIG. 6. A suitable, matching lenticular
screen can then be laminated to this reproduction so that the
picture can be seen in stereoscopic relief. If, on the other hand,
a piece of lenticular film is placed at F, the lenticules on the
film matching, to an appropriately reduced scale, those on the
screen S, the transposition process is rendered unnecessary. This
is due to the fact that the additional image-inversion caused by
the lenticules on the film results in the elementary images
becoming oriented as represented in FIG. 5. However, this is
difficult to accomplish in practice owing to the high degree of
precision with which it is necessary for the lenticules on the film
to be matched with those on the screen S.
Mechanical Amplification of Stereoscopic Base
In the applicant's U.S. Pat. No. 2,572,994 (corresponding to
British Pat. No. 656,165) there is a description of a type of
camera mounting so designed that a camera supported thereon can be
moved laterally through a predetermined distance during the
exposure period. This mounting is intended primarily for use in the
taking of stereoscopic photographs of the type known as parallax
panoramagrams. However, a mounting of this nature, or a simplified
form thereof, can be usefully adapted to form a feature of the
present invention as described below.
FIG. 13a is a schematic plan view representing a piece of
lenticular film L being exposed to light entering through the
vertical slit S in a focal-plane shutter F. The angular field of
the lenticules is denoted by .theta.. It is to be imagined that the
film and shutter are contained within a suitable piece of
photographic apparatus or camera as discussed earlier in the
specification. It is to be assumed, further, that the apparatus,
supported on a suitable mounting, is transported laterally from
position I to position II during the time taken by the shutter slit
to traverse the width of the film format. In this pair of diagrams
the film and shutter slit are depicted as moving in the same
direction. In consequence, extreme leftward images of the scene are
recorded on the left-hand edge of the film, and extreme rightward
images are recorded on the right-hand edge, just as if the film had
remained stationary during exposure. However, the horizontal
parallax or stereoscopic base has been increased by an amount equal
to the distance through which the film has moved. In the example
illustrated, the width of the film is denoted by w, and the
distance through which it has moved amounts to 3w; hence, the
stereoscopic base has been increased from w to 4w. The orientation
of the elementary images is as indicated in the earlier diagram,
FIG. 2, so that the integral photograph is pseudoscopic. Hence, in
order to produce an integram of the type represented in FIG. 6,
transposition about one axis must be performed. If an integram of
the type represented in FIG. 5 is required, transposition must be
performed about two axes.
FIG. 13b is a diagram similar to FIG. 13a, but in this case the
film and the shutter slit are represented as moving in relatively
opposite directions. As a result of this arrangement, extreme
leftward views of the scene are recorded on the right-hand edge of
the film, and extreme rightward views are recorded on the left-hand
edge. In this case, the resulting stereoscopic base is equal to the
distance through which the film has moved minus the width of the
film, amounting, in the example illustrated, to 3 -w=2w. An
important consequence of this type of arrangement is that a contact
(emulsion-to-emulsion) print from the original photograph results
in the production of an integram of the form presented in FIG. 6,
transposition about the horizontal axis having been already
accomplished during the photographic operation. Further
transposition, about the vertical axis, results in the production
of an integram of the type represented in FIG. 5.
With photographic systems of the type under discussion it is
necessary to ensure that no perceptible image-smear results from
the lateral movement of the film. The principal requirements
are:
1. The parallax angle should not be excessive,--generally not more
than about 15.degree. to 25.degree. in the case of the nearest
foreground object. That is to say, the angle subtended at any point
in the scene or subject by the total stereoscopic base line should
not be greater than about 15.degree. to 25.degree..
2. The slit in the focal plane shutter should be narrow,--generally
not wider than the lenticular pitch distance, although the slit may
have a width in excess of this limit if the parallax angle is small
and the lenticular pitch is fine.
Aerial Photography
The principle described in the preceding section can be usefully
applied to integral photography from a moving vehicle, such as an
aircraft or a spacecraft. In this case, however, the mounting
referred to above is not required, the translatory movement of the
film relative to the subject (e.g., terrain) being effected by the
forward motion of the vehicle. It is preferable for the
photographic equipment to be supported in a mounting which pivots
in such a manner that, throughout the exposure period, an imaginary
straight line extending from the center of the film format, and
normal to the surface thereof, passes through substantially the
same point in the target or scene being recorded. The mounting can
be stabilized, by methods known to those conversant with the art,
to minimize the effects of undesired motion of the vehicle, such as
pitch, roll and yaw.
The direction of motion of the focal plane shutter slit should be
substantially parallel to the flight axis. Further, in order that
the film may be viewed stereoscopically, and not pseudoscopically,
immediately after processing, the shutter slit should move in a
direction opposite to the direction of flight.
Having fully described my invention, it is to be understood that I
am not to be limited to the details herein set forth but that my
invention is of the full scope of the appended claims.
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